The proposed research will investigate the effects of body orientation on spatial cognition. Rotation and simulated rotation of the head on trunk temporarily relieve the symptoms of unilateral neglect, but it is not clear why these procedure have these effects or if such effects extend to regions of space that are represented according to different coordinate systems. In three experiments, the performance of neurologically intact individuals and patients with unilateral neglect will be assessed on three common measures of hemispatial attention: subjective midline, line bisection, and target detection. To determine the effects of body orientation on spatial cognition, subjects' performance while their heads and trunks are aligned will be compared to their performance while their trunks are rotated 15 degrees to the left, relative to their heads. In order to investigate whether this manipulation has the same effect across two regions of space, each task will be presented both in peripersonal space (i.e. space within reaching distance that is thought to be represented in face-centered coordinates) and extrapersonal space (i.e. space beyond reaching distance that is thought to be represented in trunk-centered coordinates). To explore whether manipulation of body orientation affects early attentional processes or later action selection processes, subjects' event-related brain potentials will be recorded during the target detection task. The results will provide information about the mechanism by which trunk rotation temporarily relieves the symptoms of unilateral neglect, thereby providing a basis for the development of theoretically- grounded methods for rehabilitating patients.